This invention relates to a solid state disk system, and especially a solid state disk system having a non-volatile electrically erasable and programmable read only memory which has blocks erased at the same time.
Traditional low cost mass computer storage systems have used a mechanical device employing magnetic storage media, such as a hard disk drive. The hard disk drive has predetermined memory blocks, each including a number of sectors. A disk surface of the hard disk drive is mechanically damaged sometimes during a manufacturing stage and installation in the computer system. Where the damaged disk surface is out of the scope of the permitted level, it is treated as a defect inhibiting data read and data write operations. The predetermined numbers of memory blocks of the memory system should be operated as a non-defective blocks even if there is such defect. Therefore, a non-defective spare block is assigned as a substitute for the defective block. This treatment is called a replacement. Information of the defective block (hereinafter xe2x80x9creplacement informationxe2x80x9d) should be stored and used during the replacement.
The replacement information includes information of a presence of the defect and an address of the replaced spare block. The replacement information is stored in memory media such as a RAM (Random Access Memory) controlled by a CPU (Central Processing Unit) of a micro-controller. In the case of the replacement information being stored in the RAM, a memory region for storing the replacement information is ensured in the hard disk drive or a back up electric power source for the RAM is required. Further, the replacement information should include information recorded during the manufacturing stage of the hard disk drive as well as replacement information newly found in an operation of the hard disk drive which should be additionally recorded. However, the additionally recorded information cannot be stored in the RAM.
Instead of the RAM, a non-volatile electrically rewritable memory such as a flash EEPROM is used for storing the replacement information. In such case, the flash EEPROM has a memory region divided into a number of blocks, each of which is erased at the same time. The memory region of the flash EEPROM includes a user block region storing user data, a spare block region having a spare block storing data of the defective block of the user block region, and a replacement information region storing information about an address of the spare block corresponding to the defective block where the defective block is present. Each one of the blocks in the user block region is comprised of a number of sectors, such as 16 sectors. Each of the sectors includes a header portion and a data portion. The header portion stores a code indicating a validity of the sector and a number of rewriting. The data portion stores data accessed from a host computer.
Where the header portion of the solid state disk system employing the EEPROM is defective or has an error, a normal access from the host computer cannot be ensured. In order to evade such error, an error checking and correction (ECC) region is exclusively ensured in the header portion. However, the ECC region makes the hardware larger. Further, where the replacement information region of the solid state disk system employing the EEPROM is defective or has an error, a normal access from the host computer cannot be ensured, either.
With the foregoing in view, it is therefore an object of the present invention to provide a solid state disk system being capable of access from the host computer where the header portion is defective.
For achieving the above object, a solid state disk system comprises a host interface for inputting data from and outputting data to a host computer located outside of said solid state disk system, a buffer memory coupled to the host interface for temporally storing data, an EEPROM coupled to the buffer memory, a micro-controller coupled to the host interface and buffer memory for controlling a replacement procedure. The EEPROM has a memory region divided into a plurality of blocks, each of which is erased at the same time. The memory region has a user block region storing data accessed from the host computer, a spare block region storing data from the outside for replacing any defective block within the user block region, and a replacement information region storing information about an address of a spare block corresponding to the defective block. The solid state disk system further comprises a header controller coupled to the micro-controller and EEPROM for writing a same information whether the block is defective in each header portion of sectors of the user block region.
Typical ones of various inventions of the present application have been shown in brief. However, the various inventions of the present application and specific configurations of these inventions will be understood from the following description.